Light-metal alloy and method of making same



Patented. Jan. 13,1931

UNITED STATES PATENT OFFICE EDWARD c. noanicx, or MIDLAND, MICHIGAN, ASSIGNOB TO THE DOW onEMicAL COMPANY, or MIDLAND, MICHIGA1\T, A CORPORATION OF MICHIGAN LIGHT-METAL ALLOY AND METHOD OF MAKING SAME No Drawing.

The constitution and method of making certain alloys of manganese with magnesium in which the magnesium largely predominates are disclosed in Patent No. 1,377,374 issued to W. R. Veazey May 10, 1921, and

in a companion patent to the same inventor I have found that a similarly relatively small percentage of manganese, with or Without copper. materially lmproves for certain purposes the well known class of magiie'sium alloys in which aluminum is the principal alloying element.

The present invention then consists of the new alloy product containing magnesium and aluminum in approximately the proportions stated and in addition thereto a relatively small percentage of manganese or copper and 5 manganese. The invention also comprehends the steps involved in the making of such al-' loys. all as hereinafter fully described and particularly set forth in the claims, it being understood that the following description sets forth'but several of the various'ways in which the invention may be carried out. Magnesium alloys containing not less than 80 per cent. and not more than 99.5 percent. of'magnesiun'i and not more than 20 per cent. or less than 0.5 per cent. of aluminum. are

escribed in Patent No. 965,485 issued tdG. Pistor et al.. Jplyitwl'fl'lflfand the specific prgport ions' illustrated in the example given in this patent viz. 92 per cent. of magnesium and 8"per cent. of aluminum. have been found for many purposes most satisfactory. I have discovered, however, that the addition of manganese in an amount less than one per cent exercises a beneficial influence on an alloy of this type, particularly as to the grain structure of castings made therefrom, as well as in other physical characteristics. Even a more marked improvement is effected where copper in approximately thesamesmall alloy, this may be EICCOlllPllSllQd CltllGPd'fl't' Application filed December 11, 1924; SeIiaI No. 755,166.

amountis added to the alloy along with such manganese.

Where manganese alone is to be added to a inagnesiuni-aluminum alloy of the type described. I preferably employ the method disclosed in the aforesaid Patent No. 1,377,374. For example. a measured quantity of the magnesium-aluniiiium alloy is melted up and then a limited quantity of anhydrous inanganous chloride (LIIUCIQ) is added thereto. A flux of slightly greater specific gravity than the molten magnesium metal and having a suflicicnt surface tension to cause it to form a film thereover and thus prevent exposure of the metal to the atmosphere is used in the crucible or melting pot, and when the anhydrous manganous chloride is added this flux is pushed'aside for the purpose of permitting the chloride to come directly into contact with the molten metal. The chloride is thereupon immediately reduced and the resultant metallic manganese subject to certain losses, becomes alloyed with the magnesium and aluminum. The addition of manganous chloride calculated to provide 0.5 per cent of manganese in the resultant alloy will g ve, as a matter of fact, an alloy containing approximately 0.2 per cent.

'l-Vhere in addition to such small percentage of manganese a corresponding small percentage of copper is tobe added so as to make magnesium-aluininum-copper-manganese adding to a ineasuredlqu:iutityof the magnejllllhalmi'll'nfilll base in molten condition t lie'proper small amount of cupro-nianganesc or by firstjadding such cupro-mangancseto the molten n'iagncsium alone, and then .adding aluminum to the resultant magnesium-copper-inangaiiesc alloy. Cupro-nianganese is aknown alloyof the two metals in-- volved ordinarily continuing seven parts of copper .to'three parts of manganese, and

when added in the proportion of one per cent to magnesium alone or to a previ(')usly -prepared magnesiuiu-aluminum alloy of the type hereinbefore referred to, will produce a resultant alloy in which the amount of manganese is slightly reduced as a result of apparently-unavoidablelosses, so that the cent of copper and 0.20 per cent of manganese and add thereto three successive quantities -of six ounces each of aluminum. The analyses of the resultant quarternary alloys will then show aluminum in approximately of approximately ninety three per cent.

magnesium, six per cent. aluminum, seventenths of one per cent. of copper, and onethe following amount viz., 1.84 per cent, 3.84 per cent and 5.97 per cent, respectively, the relative proportions of copper and manganese remaining substantially unchanged from the figures just given. Bars cast from such quarternary alloy and machined for test purposes show a Brinnell hardness of slightl less than 70 and yield points successive y increasing with the amount of aluminum present from approximately 9000 pounds for the 1.84 per cent aluminum contents to approximately 11,000 pounds forthe 3.84 per cent aluminum content, and approximately 12,000 pounds for the 5.97 per cent aluminum content.

An alloy similar to the foregoing but containing an aluminum content of between 8 and 8.5 per cent showsa somewhat increased Brinnell hardness and a considerably increased yield point viz. approximately 15,000

pounds. As previously indicated, for most purposes this may be regarded asthe alloy composition of the type described herein as new.

, Other modes of applying the principle of 49 my inventionmay be em loyed instead of the one explained, change eing made as regards the composition and method herein disclosed, provided the ingredients or steps stated by an of the following claims or the 5, equivalent 0 such stated ingredients or steps be employed.

" dtherefore particularly point out and distinctl claim asmyi'nventionz V 1. e method of making mluminum 50 copper-manganese alloy of magnesium, X

which comprises forming an allo of magl V, nesium and aluminum in which 1; 'e'inagnesium largely redominates, and'incorporating in such a loy in molten state, a' cupromanganese alloy.

2. As a new product, an alloy containing 7 magnesium in excess of eighty per cent., manganese in an amount not exceeding fivetenths of one per cent., and the balance prin- I v u 00 cipally aluminum with a relatively small amount of copper.

3. As a new product, a magnesium-aluminum-copper-manganese alloy wherein the magnesium is in excess of eighty per cent., the copper not exceeding two per cent'., the

quarter of one per cent. of manganese. Signed by me this 5th day of December,

EDWARD C. BURDICK. 

